This application claims the priority of German patent document 102 48 633.6, filed 18 Oct. 2002, the disclosure of which is expressly incorporated by reference herein.
The present invention relates to a method of controlling the rotational speed of a drive unit, particularly an internal-combustion engine generator unit.
To control the rotational speed of a drive unit, a first rotational-speed controlling device is provided to control the idling speed, together with a second rotational-speed controlling device to control the final speed. (As used herein, the term xe2x80x9cdrive unitxe2x80x9d applies to an internal-combustion engine generator unit as well as to an internal-combustion engine transmission unit.) To control the rotational speed of the drive unit, the dominant controlling device computes a control variable, such as an injection quantity, from a desired-actual comparison. However, the reaction times of such a control circuit structure in the case of a sudden load change, and the transition from the first to the second controlling device or vice-versa, are problematic in that undesirable overswings may occur.
To improve the performance of such a system in this regard, according to German Patent Document DE 197 11 787 A1, in the case of small control deviations, the first controlling device is dominant, while the second controlling device is dominant in the case of large control deviations. To reduce the overswings, during the transition from the second to the first controlling device, the integrating fraction of the first controlling device is initialized. Regardless of which of the two controlling devices is dominant, both simultaneously compute their respective control variables, which results in high computing expenditures. Likewise, it is a problem that, except by defining the desired value, the operator of the drive unit can exercise no direct influence, for example, during the starting operation.
One object of the present invention is to provide a method of controlling the rotational speed of a drive unit, in which the starting operation is also taken into account.
This and other objects and advantages are achieved by the method and apparatus according to the invention in which a third controlling device is provided for computing a third injection quantity to control the rotational speed of the starting operation. In addition, the user of the drive unit can directly intervene by defining a charge, and the charge definition is used to compute a charge injection quantity which is compared with the injection quantity of the dominant controlling device. Based on the comparison, either the dominance of the controlling device is retained or the charge definition is set to be dominant for a power-determining signal. (In the sense used herein, the power-determining signal is either an injection quantity or the control path of a control rod.)
According to the invention, the controlling devices which are not dominant are deactivated. Because only the dominant controlling device is therefore active, a clear software structure is achieved, and computer capacity is freed.
In the case of an internal-combustion engine generator unit, the first controlling device controls idling rotational speed, while the second controls final rotational speed and the third controls starting rotational speed. The first injection quantity is the idling rotational speed injection quantity; the second injection quantity is the final rotational speed injection quantity; and the third injection quantity is a starting rotational speed injection quantity. In the case of a dominant charge definition, it is checked as a function of the actual rotational speed of the drive unit whether the idling rotational speed controlling device or the final rotational speed controlling device is activated. During a change, for example, to the idling rotational speed controlling device, its integrating fraction (I-fraction) is initialized, which achieves low overswing ranges during the transition.
During a starting operation, initially the starting rotational speed controlling device is dominant, and a check is made whether the charge injection quantity is larger than the starting rotational speed injection quantity. Based on the result of this comparison, the end of a starting condition is detected, and the idling rotational speed controlling device is then set to be dominant as the charge definition. Due to the possibility of a charge definition as early as in the starting operation, a faster run-up of the drive unit is achieved.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawings.